#!/bin/bash
# does work
#expr 2 * 3
i=2
i=$[$i+1]
echo $i

#expr \(2 * 3\)
#a=expr 2*3
#echo $a

i=1; while [ $i -le 5 ]; do echo $i; i=$[ $i + 1 ]; done

exit

###################
# does not work

#!/bin/bash
# does not work because of spaces in add-expression
expr 2 * 3
i=2
i=$[ $i + 1 ]
echo $i

#expr \(2 * 3\)
#a=expr 2*3
#echo $a

#i=1; while [ $i -le 5 ]; do echo $i; i=$[ $i + 1 ]; done